Air actuated disc brakes are frequently used on heavy vehicles. The configuration of these brakes varies. One type of disc brake of the prior art is described in EP0684403.
The disc brake described in EP0684403 has an outboard brake pad and an inboard brake pad. A brake disc is positioned between the two brake pads. A single pressure spindle is positioned in a housing of a brake caliper and is operable to push the inboard brake pad towards the brake disc. The brake disc is fixed in an inboard-outboard direction, such that movement along an axis perpendicular to a principal plane of the brake disc is prevented. This arrangement is such that when the inboard brake pad is pushed towards and contacts the brake disc this causes the caliper to move inboard. As the caliper moves inboard it moves the outboard brake pad towards the brake disc clamping the brake disc between the outboard and the inboard pads and thereby effecting braking by frictionally inhibiting rotation of the brake disc.
The pressure spindle is guided by a yoke which is positioned within the housing of the caliper. A lever is operable to slide the yoke within the housing, so as to move the pressure spindle and inboard brake pad towards the brake disc. Four elongate projections are formed on the surface of the yoke and on the surface of the housing, and are provided as a guidance system to guide the yoke when sliding in the housing.
One disadvantage of such a guidance system is the difficulty of manufacturing the projections to the required close tolerance. A further disadvantage of the system is that it is susceptible to wear over the life of the disc brake.